Identification

Archispirostreptus gigas is one of the largest millipede species on Earth, with adults reaching 33–38 cm (up to about 15 inches) in exceptional individuals, though 20–28 cm is more typical in captivity. The body is cylindrical and smooth, dark brown to near-black with slightly paler inter-segmental membranes that give the body a faintly banded appearance in good light. Legs are numerous — adults carry well over 300 — and move in the characteristic flowing wave pattern of all millipedes.

Females are typically larger and more robust than males. Males possess modified gonopods on the seventh body segment which can be used to confirm sex, though this requires careful handling and a good eye. A newly adopted animal of unknown sex can often be estimated by size — larger, heavier-bodied individuals are usually female.

Natural History

Archispirostreptus gigas is native to East Africa, with its range centered in the coastal lowland forests and scrublands of Kenya and Tanzania, extending into parts of Mozambique. It occupies humid forest floors, living among deep leaf litter, rotting logs, and soil, where it plays a key ecological role as a detritivore — breaking down dead plant material and returning nutrients to the soil.

In the wild, populations are subject to distinct wet and dry seasons. The dry season triggers a form of dormancy: animals burrow into the soil and seal themselves inside a mucus-lined chamber to wait out the drought. In captivity, a slight reduction in humidity during a simulated dry season (a few weeks of drier conditions) is sometimes recommended to encourage breeding behavior, though this is not strictly necessary for routine care. Lifespan in captivity is typically 5–7 years, though some individuals have lived longer.

This species was historically imported into the pet trade in large numbers, but wild collection has been restricted; most animals available in the hobby today are captive-bred or long-term captive individuals. If adopting, ask about the animal's origin and age if possible.

Defense Secretions

Like all millipedes, A. gigas produces benzoquinone secretions from repugnatorial glands along the body when stressed. These are significantly less potent than in some other millipede orders — this species is generally considered one of the milder in terms of secretion strength, which is part of why it's recommended as a starter species. A calm, well-acclimated animal handled gently is unlikely to secrete at all. The secretions smell faintly of almonds or chemicals and can leave a yellowish stain on skin.

Enclosure

Adults need significant floor space — these are large animals that move more than most people expect. A 40-gallon breeder tank (36" × 18" footprint) is a solid minimum for a single adult. Larger is always better. Height is less critical than footprint, though some depth is needed to accommodate substrate.

Temperature

Target 75–80 °F (24–27 °C). Unlike my Tylobolus uncigerus, this is a tropical species that needs warmth year-round — typical Portland room temperatures are likely too cool, especially in winter. A heat mat on the side (never the bottom, which can overheat substrate and trap the animal) or a low-wattage ceramic heat emitter on a thermostat is the safest approach.

Keep the heat source on one side only — the other side of the enclosure should be at ambient room temperature, giving the animal a thermal gradient to self-regulate. Never let the enclosure exceed 85 °F.

Substrate

Substrate is the most important aspect of millipede husbandry — it is simultaneously shelter, humidity regulator, and the primary food source. The majority of a millipede's diet (upwards of 80%) comes directly from consuming substrate, which means an indigestible filler doesn't just waste space — it displaces actual food. Avoid coconut coir entirely: it cannot be broken down by the millipede's gut microbiome and causes impaction (Kevin Nasser, Boogie Down Bugs, 2023).

The gold standard base is flake soil — hardwood that has been fermented long enough for its cellulose structure to break down into something millipedes can actually extract nutrition from. It can be purchased from specialist invertebrate suppliers or made at home (see DIY note below). Flake soil can be mixed with plain unfertilized topsoil to fill larger enclosures and supplemented with decaying wood chunks and deep leaf litter.

Sterilize any field-collected material before use: bake at 250 °F for 30–40 minutes (allow to cool completely) or freeze for 48 hours. This clears mites and parasites without destroying organic structure.

Humidity & Moisture

Target 75–80% relative humidity. The substrate should feel like a well-wrung sponge throughout — moist but not waterlogged, and never bone dry. Mist one side of the enclosure every 2–3 days with dechlorinated or distilled water, leaving the other side slightly drier as a gradient. A water dish is not necessary — moisture needs are fully met through misting and the substrate moisture content. Monitor with a digital hygrometer placed mid-level in the enclosure.

Good ventilation and high humidity work together here, not against each other. Stagnant high humidity is what causes mold and bacterial growth — moving air at high humidity is what replicates the forest floor. Watch for excessive condensation on walls; wipe it down if it pools. Monitor with a digital hygrometer placed mid-level in the enclosure.

Feeding

At least 80% of a millipede's diet is the substrate itself. This is worth internalising, because it changes how you think about supplemental feeding — fruits and vegetables are treats, not the main course. A well-maintained, nutritious substrate is the feeding. That said, supplemental food does matter, particularly protein, which is often underemphasised in hobbyist guides.

The millipede exoskeleton is chitin-based and requires protein as well as minerals to build and maintain properly. Weekly protein supplementation is recommended for most species; for a large animal like A. gigas, twice weekly is not excessive. Good protein sources cover the mineral requirements as well, making separate calcium supplementation largely redundant if protein is offered consistently (Kevin Nasser, Boogie Down Bugs, 2023).

Remove uneaten soft food within 24–48 hours to prevent mould. Fish flakes and cuttlebone can remain indefinitely. A water dish is not necessary — moisture needs are met through misting and the substrate itself. Don't be alarmed if she goes off food briefly after being moved; rehoming stress typically resolves within a week or two.

Moulting & Growth

Millipedes moult throughout their lives, adding segments and legs with each shed until reaching sexual maturity, after which adults continue to moult but without adding segments. A moulting A. gigas will burrow deep into the substrate and may disappear entirely for 2–6 weeks. Do not disturb. Do not probe the substrate. Do not panic.

After emerging, a freshly moulted millipede will be soft and pale for several days. It will consume its shed exuviae — do not remove the shed. It will also be more sensitive and more likely to secrete during this period. Wait at least a week before handling again. Ensure calcium is available in the enclosure during this time, as the exoskeleton needs to harden fully.

Handling

Archispirostreptus gigas is widely considered one of the most handleable millipede species — calm, slow-moving, and generally tolerant of gentle interaction. That said, all handling should still be kept brief and low-stress. Let the animal walk across your hands rather than grasping, and keep yourself close to the ground in case of a fall. A dropped millipede can be seriously injured.

Watch for defensive coiling (they'll curl into a spiral), which signals stress — return the animal to the enclosure and let them decompress. Secretions may follow coiling; wash hands immediately. Avoid handling during or just after moulting. Avoid handling when you have chemicals, strong scents, or hand lotion on your skin.

Cycling & Breeding

While A. gigas will mate readily in captivity, getting females to lay viable eggs requires mimicking the wet/dry seasonal cycle of East Africa. This isn't necessary for simply keeping a single animal — but it's worth understanding the biology, and a natural cycle can benefit health even outside of breeding context.

East Africa experiences distinct wet and dry seasons. In most of the range (Kenya, Tanzania, Mozambique), dry months fall roughly July–September, with wet months in late April through June and again in October–November. Captive cycling attempts to replicate this:

The deep substrate and thick leaf litter layer are critical during cycling — during the wet season, animals move upward away from the saturated lower substrate; during the dry season, they burrow down to find retained moisture. Neither survival strategy works without depth. The female will lay eggs during the transition between seasons; juveniles grow very slowly and take approximately 5 years to reach sexual maturity (Kevin Nasser, Boogie Down Bugs, 2023).

Health & Common Issues